Major spoilers ahead for Avengers: Infinity War. Like all other movies in the Marvel Cinematic Universe, Infinity War ends with a secret scene after the closing credits. Though Samuel L. Jackson's S.H.I.E.L.D. Agent Nick Fury doesn't appear in the rest of the movie, he and fellow Agent Maria Hill play a big part in this final scene. But the major surprise hinted at after the closing credits is Marvel's first solo female superhero, Captain Marvel. Brie Larson's upcoming superhero Captain Marvel doesn't actually appear in the closing credits, but her symbol shows up on an old-school pager used by Fury. But what did Nick Fury send to Captain Marvel at Infinity War's end? And what does her response mean for Avengers 4?
At the end of Infinity War, Thanos has actually succeeded in acquiring all six of the infinity stones, needed to accomplish his master plan to "save the galaxy" by wiping out half of its population. "If life is unchecked it will cease to exist," he says. With his gauntlet firmly in hand, Thanos snaps his fingers and half of the population of the galaxy, including half of our beloved Avengers, disintegrate into dust before our very eyes. So essentially, Infinity War kills off half of its superheroes, which is pretty intense, to say the least.
But this is Marvel, after all — half of the MCU can't possibly stay dead, right? That's where Captain Marvel, and time travel, come into play. It's pretty much assumed that both the upcoming Captain Marvel and Avengers 4 are going to involve some kind of time travel. It's already made an appearance in the MCU movies, considering Dr. Strange has a hold of the Time Stone. Both he and Thanos use it to manipulate time to their advantage. And, as we know, Captain Marvel is going to be the earliest Marvel movie chronologically (after Captain America: The First Avenger), taking place way before even the events of the first Iron Man movie, back in the early 1990s.
So Nick Fury's message to Captain Marvel might've gone through time. The machine he uses to send it looks kind of like an old clunky beeper or pager. It's not as high-tech as some of the other S.H.I.E.L.D. gear, and it's definitely not just a regular cell phone. Could it be some kind of inter-dimensional or time-bending messaging device? Did Fury send an S.O.S. back in time to the one superhero that can save them? Considering the disastrous events of the finale of Infinity War, the only possible way to undo the multitudinous deaths in the movie would be to travel back in time somehow and undo Thanos' destructive snap. But considering the villain has the Time Stone, how else could it be done?
That's where Captain Marvel might come in. The standalone Captain Marvel movie, which will hit theaters in March 2019, will probably revolve around how fighter pilot Carol Danvers obtains her super powers. It's not clear what her powers are yet, considering that she's getting a whole new origin story, but it's possible they involve the bending of time or the creation of alternate dimensions. The current theories suggest that Danvers finds herself in the middle of giant battle between the Kree, the alien race seen in Guardians of the Galaxy, and the Skrull, whom we haven't met in the movies but who are known for infiltration and impersonation. This makes it sound like some more well-known characters of the MCU might actually be revealed as Skrull in Avengers 4, which comes only a couple of months after Captain Marvel in May 2019.
It is known that Captain Marvel spends a lot of time, many years in fact, out in space, so her return to Earth could involve some kind of alternate timeline or backward mobility of some sort. Either way, we're going to have to unfortunately wait over a year to find out what exactly Fury sent to Captain Marvel and if she can find a way to alter time and save the Avengers for good.